For those of you who are anti-antipersperant of any kind, or advocates of "natural" deodorants sans aluminum, the following information probably isn't worth your time or will just fire you up unnecessarily. But for those who use good ol' antiperspirant, I just learned that according to some scientific evidence, it's probably more effective to put the stuff on at night before you go to bed. From Lifehacker:
Antiperspirant[…] is designed to temporarily plug your sweat pores and reduce the amount of perspiration expelled, keeping your armpits dry (and thus inhibiting odor-causing bacteria growth).
When you are less active (sleeping), your body temperature drops, causing you to sweat less. This lack of moisture enables your body to more readily absorb the active ingredient in most antiperspirants—aluminum—as Dr. David Pariser, president of the American Academy of Dermatology, explained to Consumer Reports. (It's easier for the aluminum to penetrate the skin when it doesn't have to wade through the very thing it's working against.) Overnight, your skin will have more time to absorb the antiperspirant, making it more effective than if you apply it immediately before rushing around to get ready for the day.
A morning shower won't wash most of it away either.